Alpha-numeric displays are produced in many forms which are operated by electrical signals usually provided by an electronic control circuit. Such displays are attractive and versatile but usually they are volatile. That is, they do not retain their state when the electrical signal is removed. The use of a nonvolatile memory in conjunction with such a volatile display increases the cost of the display by an amount which is often prohibitive. Even if such a memory is provided the display is not active when electrical power is turned off. Still many applications require nonvolatile displays as well as nonvolatile memories. For example, the odometer of an automotive vehicle must reliably accumulate distance information and retain that information even though the vehicle battery is removed for servicing or the electrical power is otherwise interrupted. The mechanical number wheel odometer driven by an electrically actuated stepper motor accomplishes the purpose of a nonvolatile display responsive to an electrical input, but such a device consumes an objectionable amount of space and is limited in its versatility.
It is therefore an object of the invention to provide a nonvolatile display which is responsive to an electrical signal, is compact and in addition requires no expensive nonvolatile memory element. It is a further object to provide such a display which serves as a nonvolatile memory.